On the whole, conductive carbon nanomaterials, such as carbon nanotubes, graphene, carbon fibers, carbon black and so forth, find applications in a variety of fields including transparent electrodes, antistatic finishing, electromagnetic wave shielding, electrodes for energy generation and energy storage devices, heat dissipation materials, conductive fibers, sensors, emitters, X-ray light sources, etc. For use in forming an electrode by use of a printing technique or in preparing fibers, a highly concentrated dispersion or spinning dope of conductive nanomaterials in a paste form is needed. Application of such conductive carbon nanomaterials to transparent electrodes requires a relatively dilute coating solution of the carbon nanomaterials that exhibits superior dispersibility.
In this regard, a surfactant or a dispersant, such as a copolymer, ionic liquid, etc., is requisite for preparing a coating solution or paste of conductive nanomaterials. Of course, when excessive functional groups are introduced onto the surface thereof, conductive materials can be easily dispersed, but lose their conductivity.
Further, the electroconductivity of carbon nanomaterials can be extremely increased when even a small amount of a metal nanomaterial having a one- or two-dimensional structure is added thereto. However, only when the carbon nanomaterial in mixture with the metal nanomaterial keeps its dispersibility high, can it be applied to transparent electrodes, conductive fibers, energy electrodes, etc.
Therefore, if a conductive nanomaterial-based paste keeps high dispersibility without using a dispersant, hybridization of the conductive nanomaterial-based paste with a metal nanomaterial brings about an improvement in conductivity, production cost and process simplification as well as allowing for substitution for conventional electrode materials. Given, a carbon nanomaterial/metal nanomaterial hybrid that is able to disperse in an organic solvent even in the absence of an aqueous dispersant further has the advantage of enabling combination with various materials that are feasibly compatible to an organic solvent, including polymer binder materials, metals, and metal oxides.
However, thus far nowhere has the preparation of a coating solution based on the hybridization of a carbon nanomaterial with a metal nanomaterial without using a dispersant been reported.